A liquid crystal display device utilizes optical anisotropy, dielectric anisotropy and so forth of a liquid crystal molecule in a liquid crystal composition. A classification based on an operating mode for the liquid crystal molecules includes a phase change (PC) mode, a twisted nematic (TN) mode, a super twisted nematic (STN) mode, a bistable twisted nematic (BTN) mode, an electrically controlled birefringence (ECB) mode, an optically compensated bend (OCB) mode, an in-plane switching (IPS) mode, a fringe field switching (FFS) mode and a vertical alignment (VA) mode.
A liquid crystal display device having a mode in which a polymer is combined with the liquid crystal composition is known. Examples of the modes include a polymer sustained alignment (PSA) mode or a polymer stabilized (PS) mode. In the liquid crystal display device having the mode, the liquid crystal composition to which a polymerizable compound is added is injected into a display device. The display device is irradiated with ultraviolet light in a state of applying voltage between electrodes to polymerize the polymerizable compound, and thus the polymer is formed in the liquid crystal composition. According to the method, a liquid crystal display device in which a response time is shortened and image persistence is improved is obtained.
The method can be applied to liquid crystal display devices having various operating modes, and such modes are known as a PS-TN mode, a PS-IPS mode, a PS-FFS mode, a PSA-VA mode and a PSA-OCB mode. The polymerizable compound to be used in the device having such a mode is considered to have high capacity for aligning the liquid crystal molecules, but solubility in the liquid crystal composition is far from high. An attempt has been so far made on improving the solubility in the liquid crystal composition, but as the solubility is improved, polymerization reactivity tends to decrease. Therefore, development has been desired for a polymerizable compound having a suitable balance between the solubility and the polymerization reactivity.